Support vector machine based high speed protection relay for EHV/UHV transmission line

Abstract

This paper presents a fast and accurate relaying technique for a long 765kv UHV transmission line based on support vector machine. For a long EHV/UHV transmission line with large distributed capacitance, a traditional distance relay which uses a lumped parameter model of the transmission line can cause malfunction of the relay. With a frequency of 1kHz, 1/4th cycle of instantaneous values of currents and voltages of all phases at the relying end are fed to Support Vector Machine(SVM). The SVM detects fault type accurately using 3 milliseconds of post-fault data and reduces the fault clearing time which improves the system stability and power transfer capability. The performance of relaying scheme has been checked with a typical 765kV Indian transmission System which is simulated using the Electromagnetic Transients Program(EMTP) developed by authors in which the distributed parameter line model is used. More than 15,000 different short circuit fault cases are simulated by varying fault location, fault impedance, fault incidence angle and fault type to train the SVM for high speed accurate relaying. Simulation studies have shown that the proposed relay provides fast and accurate protection irrespective of fault location, fault impedance, incidence time of fault and fault type. And also the proposed scheme can be used as augmentation for the existing relaying, particularly for Zone-2, Zone-3 protection.Index Terms-UHV transmission line protection, Electromagnetic Transients program (EMTP), support vector machine (SVM)

A robust and accurate discrete Fourier transform‐based phasor estimation method for frequency domain fault location of power transmission lines

“…The sampling frequencies of fault recorders are fixed. As protections on both terminals of EHV and UHV lines trip rapidly after fault happens, the available data window for fault location is normally a few fundamental frequency cycles [5,6, 28]. Hence, within this time span after faults happened, the fault transient signals are mainly consisted of a fundamental frequency component, integer harmonic components and decaying DC component, and the basic fault signal model can be expressed as follows [6, 14–21, 23–27]: $$\begin{equation}f\ \left( t \right) = \mathop \sum \limits_{m = 1}^H {M_m}\cos \left( {m \cdot 2\pi {f_0}t + {\theta _m}} \right)\ + D{e^{ - \alpha t}}.\end{equation}$$…”

“…The sampling frequencies of fault recorders are fixed. As protections on both terminals of EHV and UHV lines trip rapidly after fault happens, the available data window for fault location is normally a few fundamental frequency cycles [5,6,28]. Hence, within this time span after faults happened, the fault transient signals are mainly consisted of a fundamental frequency component, integer harmonic components and decaying DC component, and the basic fault signal model can be expressed as follows [6,[14][15][16][17][18][19][20][21][23][24][25][26][27]:…”

“…To enhance robustness and improve accuracy, methods presented in [6,26,27] employ a time window of two fundamental frequency cycles to obtain accurate phasor estimation performance, which meets the requirement of frequency domain methods when the length of data window is adequate. However, in recent years, with the continuous development of power industry, high speed line protections are broadly applied to extra-high-voltage (EHV) and ultra-high-voltage (UHV) transmission lines [28,29]. The high speed relays can be tripped within 10 ms and arc extinguishing time is shortened due to fast circuit breakers, which means the fault clearance time is significantly reduced.…”